diff --git a/lower-constraints.txt b/lower-constraints.txt
index 838433d..9737eab 100644
--- a/lower-constraints.txt
+++ b/lower-constraints.txt
@@ -15,7 +15,6 @@ debtcollector==1.19.0
 decorator==4.2.1
 deprecation==2.0
 django-appconf==1.0.2
-django-babel==0.6.2
 django-compressor==2.0
 django-pyscss==2.0.2
 Django==2.2
@@ -25,9 +24,7 @@ dulwich==0.19.0
 extras==1.0.0
 fasteners==0.14.1
 fixtures==3.0.0
-flake8==2.5.5
 futurist==1.6.0
-hacking==0.12.0
 horizon==17.1.0
 idna==2.6
 imagesize==1.0.0
@@ -93,7 +90,6 @@ rfc3986==1.1.0
 rjsmin==1.0.12
 semantic-version==2.6.0
 simplejson==3.13.2
-six==1.11.0
 snowballstemmer==1.2.1
 stevedore==1.28.0
 termcolor==1.1.0
diff --git a/test-requirements.txt b/test-requirements.txt
index 4707b5f..238c00f 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -1,7 +1,7 @@
 # The order of packages is significant, because pip processes them in the order
 # of appearance. Changing the order has an impact on the overall integration
 # process, which may cause wedges in the gate later.
-hacking>=3.0,<3.1.0 # Apache-2.0
+hacking>=3.0.1,<3.1.0 # Apache-2.0
 
 coverage!=4.4,>=4.0 # Apache-2.0
 oslo.config>=5.2.0 # Apache-2.0
diff --git a/tox.ini b/tox.ini
index fddf81b..f101e7a 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,7 +1,11 @@
 [tox]
-minversion = 1.6
+minversion = 3.1.1
 envlist = py38,pep8
 skipsdist = True
+# Automatic envs (pyXX) will only use the python version appropriate to that
+# env and ignore basepython inherited from [testenv] if we set
+# ignore_basepython_conflict.
+ignore_basepython_conflict = True
 
 [testenv]
 basepython = python3